Modelling methanol and hydroxyl masers in star-forming regions

Cragg, D. M.; Соболев, А. М.; Godfrey, Peter D.

doi:10.1046/j.1365-8711.2002.05226.x

Cited by 162 publications

(273 citation statements)

References 61 publications

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“…Theoretical works treat the 1612 and 1720 MHz lines as complementary with one line being commonly inverted while, in the same volume, the other one is in absorption. In Cragg et al (2002), it is found that 1612 MHz appears in a zone of high density (n H > 10 6 cm −1 ), for a high OH column density (N OH /ΔV > 10 11 cm −3 s) and a high gas temperature T k > 100 K. However, we presume that such conditions do not apply well to K 3-35. Although they are clearly associated with K 3-35, the 1612 and 1720 MHz lines are well separated (see position offset in Table 3 and Fig.…”

Section: Remarks On Oh Pumpingmentioning

confidence: 74%

“…Elitzur et al 1976), and, more recently, the 1665 and 1667 MHz main lines (see e.g. Collison & Nedoluha 1994;Pavlakis & Kylafis 1996a,b;Cragg et al 2002). Nevertheless, theory is still uncertain because calculations of the OH populations in an expanding shell are a complex task with several competing processes which include: FIR (far infra red) pumping via the 2 Π 1/2 and 2 Π 3/2 ladders, NIR (near infra red) pumping from the radiation of the underlying star and circumstellar dust, line overlaps of FIR lines and collisional excitation through the 2 Π ladders.…”

Section: Introductionmentioning

confidence: 97%

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Discrete Source Survey of 6 GHz OH emission from PNe and pPNe and first 6 GHz images of K 3–35

Desmurs¹,

Baudry²,

Sivagnanam³

et al. 2010

A&A

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Aims. The aim of this study is to investigate the physical properties of molecular envelopes of planetary nebulae (PNe) in their earliest stages of evolution. Methods. Using the 100 m telescope at Effelsberg, we have undertaken a high sensitivity discrete source survey for the first excited state of OH maser emission (J = 5/2, 2 Π 3/2 at 6 GHz) in the direction of PNe and proto-planetary nebulae (PNe) exhibiting 18 cm OH emission (main and/or satellite lines), and we further validate our detections using the Nançay radio telescope at 1.6-1.7 GHz and MERLIN interferometer at 1.6-1.7 and 6 GHz. Results. Two sources have been detected at 6035 MHz (5 cm), both of them are young (or very young) PNe. The first one is a confirmation of the detection of a weak 6035 MHz line in Vy 2-2. The second one is a new detection, in K 3-35, which was already known to be an exceptional late type star because it exhibits 1720 MHz OH emission. The detection of 6035 MHz OH maser emission is confirmed by subsequent observations made with the MERLIN interferometer. These lines are very rarely found in evolved stars. The 1612 MHz masers surround but are offset from the 1720 and 6035 MHz masers which in turn lie close to a compact 22 GHz continuum source embedded in the optical nebula.

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Section: Remarks On Oh Pumpingmentioning

confidence: 74%

Section: Introductionmentioning

confidence: 97%

Discrete Source Survey of 6 GHz OH emission from PNe and pPNe and first 6 GHz images of K 3–35

Desmurs¹,

Baudry²,

Sivagnanam³

et al. 2010

A&A

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“…That we find statistically different dust temperatures between sources showing excitedstate OH masers compared to the other maser types, as well as 6.7-GHz methanol masers with and without accompanying 12.2-GHz methanol masers, gives us a unique opportunity to compare with maser models (e.g. Cragg, Sobolev & Godfrey 2002. water Figure 12.…”

Section: Comparison With Maser Modelsmentioning

confidence: 77%

The 6-GHz Multibeam Maser Survey – III. Comparison between the MMB and HOPS

Breen

Contreras

Ellingsen

et al. 2017

Monthly Notices of the Royal Astronomical Society

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We have compared the occurrence of 6.7-GHz and 12.2-GHz methanol masers with 22-GHz water masers and 6035-MHz excited-state OH masers in the 100 square degree region of the southern Galactic plane common to the Methanol Multibeam (MMB) and H 2 O southern Galactic Plane surveys (HOPS). We find the most populous star formation species to be 6.7-GHz methanol, followed by water, then 12.2-GHz and, finally, excited-state OH masers. We present association statistics, flux density (and luminosity where appropriate) and velocity range distributions across the largest, fully surveyed portion of the Galactic plane for four of the most common types of masers found in the vicinity of star formation regions.Comparison of the occurrence of the four maser types with far-infrared dust temperatures shows that sources exhibiting excited-state OH maser emission are warmer than sources showing any of the other three maser types. We further find that sources exhibiting both 6.7-GHz and 12.2-GHz methanol masers are warmer than sources exhibiting just 6.7-GHz methanol maser emission. These findings are consistent with previously made suggestions that both OH and 12.2-GHz methanol masers generally trace a later stage of star formation compared to other common maser types.

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“…1) The proximity to the jets may indicate that the 6.7 GHz maser excitation could be favored by the outflow activity. One can speculate that the mid-infrared photons, required for pumping the 6.7 GHz masers (Cragg et al 2002), could more easily penetrate into the dense HMC gas in proximity of the outflows, taking advantage of the cavities induced by the outflowing gas. The proposed association of the 6.7 GHz masers with outflows, based on the similarity of the 3D velocities of the methanol and water masers, agrees with the results by De Buizer (2003) and De Buizer et al (2009), which find that in most cases the methanol masers are elongated parallel to jets traced by the H 2 and SiO emissions, suggesting a physical association of the 6.7 GHz masers with the corresponding outflows.…”

Section: Methanol and Oh Maser Dynamics: Jet-driven Expansion Of The Hmcmentioning

confidence: 99%

A double-jet system in the G31.41 + 0.31 hot molecular core

Moscadelli

Cesaroni

et al. 2013

A&A

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Context. Many aspects of massive star ( > ∼ 10 M ) formation are still unclear. In particular, the outflow properties at close distance (100-1000 AU) from a massive young stellar object (MYSO) are not yet well established. Aims. This work presents a detailed study of the gas kinematics toward the hot molecular core (HMC) G31.41+0.31. Methods. To study the HMC 3D kinematics at milli-arcsecond angular resolution, we performed multi-epoch VLBI observations of the H 2 O 22 GHz and CH 3 OH 6.7 GHz masers, and single-epoch VLBI of the OH 1.6 GHz masers. Results. Water masers present a symmetric spatial distribution with respect to the HMC center, where two nearby (0. 2 apart), compact, VLA sources (labeled "A" and "B") are previously detected. The spatial distribution of a first group of water masers, named "J1", is well fit with an elliptical profile, and the maser proper motions mainly diverge from the ellipse center, with average speed of 36 km s −1 . These findings strongly suggest that the "J1" water maser group traces the heads of a young (dynamical time of 1.3 × 10 3 yr), powerful (momentum rate of 0.2 M yr −1 km s −1 ), collimated (semi-opening angle 10 • ) jet emerging from a MYSO located close (within ≈0. 15) to the VLA source "B". Most of the water features not belonging to "J1" present an elongated (≈2 in size), NE-SW oriented (PA ≈ 70 • ), S-shape distribution, which we denote with the label "J2". The elongated distribution of the "J2" group and the direction of motion, approximately parallel to the direction of elongation, of most "J2" water masers suggests the presence of another collimated outflow, emitted from a MYSO placed near the VLA source "A". The proper motions of the CH 3 OH 6.7 GHz masers, mostly diverging from the HMC center, also witness the expansion of the HMC gas driven by the "J1" and "J2" jets. The orientation (PA ≈ 70 • ) of the "J2" jet agrees well with that (PA = 68 • ) of the well-defined V LSR gradient across the HMC revealed by previous interferometric, thermal line observations. Furthermore, the "J2" jet is powerful enough to sustain the large momentum rate, 0.3 M yr −1 km s −1 , estimated from the interferometric, molecular line data in the assumption that the V LSR gradient represents a collimated outflow. These two facts lead us to favor the interpretation of the V LSR gradient across the G31.41+0.31 HMC in terms of a compact and collimated outflow.

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Modelling methanol and hydroxyl masers in star-forming regions

Cited by 162 publications

References 61 publications

Discrete Source Survey of 6 GHz OH emission from PNe and pPNe and first 6 GHz images of K 3–35

Discrete Source Survey of 6 GHz OH emission from PNe and pPNe and first 6 GHz images of K 3–35

The 6-GHz Multibeam Maser Survey – III. Comparison between the MMB and HOPS

A double-jet system in the G31.41 + 0.31 hot molecular core

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